Spyke,
Looking Orabanda's photos, I think there might be cause for confusion, which is why I suggested measurements. If I am correct, you have a Spitfire Scrambler with no pillion loops. Therefore, knowing that the boss for the brake pin goes at the intersection of the pillion loop and the vertical frame member may not help you. If Orabanda is listening, and it is currently convenient, perhaps he can give you the needed measurements.
Richard L.